Just wondering if anyone has seen an issue like this before.
Replaced my O2 sensor because it wasn't oscillating between 0.1 and 0.9 volts. New one is still doing the same thing. When the car is cold it reads low 0.1v and when warm sits around 0.9v but doesn't move back and forth. Pressing the accelerator will make it read lower, but it should still be hunting under idle.
Saturday, January 28, 2006 - 05:07 pm, by: Mark Paddick(Sparks)
ECU not doing the stuff it should? The reading of the oxygen sensor varies because the actual fuel ratios vary. i.e. it follows what the ECU is doing. It sounds like the ECU is not going into closed loop. That may be because of a lot of factors; it won't go to closed loop until engine is warm so check temp sensors and stuff like that. Also check that the MAP sensor is functioning correctly. Or the ECU itself could be running in some sort of limp mode or just plain faulty. I'm not sure what role the catalytic converter plays in all this, perhaps a problem there. I seem to remember your car is fairly highly modified? Really big injectors could cause this sort of thing; not being able to make small changes in fuel delivery fast enough could mask the normal mixture oscillations. I would have thought the voltage reading from the O2 sensor would be lower (1/2 scale) if that were the case though. If the O2 sensor readings are in fact real and are telling you what IS happening I would be very careful about using high boost until you sort it as 0.9 volts means LEAN and the fact that two sensors give similar readings would tend to indicate that the readings are in fact real. One other thing is that some meters can load the sensor enough to give a false reading. This would give a lower than expected reading though which would make the 0.9v really scary!
Err, are you absolutely sure that 0.9v is lean? When I let off the loud pedal, the value shoots to 0v (which I would assume lean) and at idle, it sits very near 0.9v and I can literally see the fumes pour out the exhaust.
The car performs brilliantly on a dyno with ever so slightly rich numbers across the board. It's closed loop mode which isn't working, and I'm suspecting I may have buggered up the ECU at some point, which I'm not too happy about. Now to find a "spare" one to test with.
Sunday, January 29, 2006 - 07:48 am, by: Mark Paddick(Sparks)
yes you're right; got it arse about. Shouldn't do stuff really late at night! Most comments still valid though. Not as dangerous for the engine, which is good. Faulty ECU or if you're running big injectors with a standard ECU are most likely.. Which ECU is it?